Antd for Vue2实现提示框可拖拽（a-modal提示框）

老项目迭代升级提出新的需求，要求所有弹出框可随意拖拽，

接下来是实现思路

主要就是通过自定义指令实现弹出框的拖拽

1. 1. 在 utils 中新建 directives.js 文件

import Vue from 'vue'
 
// v-drag-modal: 弹窗拖拽
const dragModal = (el, bindings, vnode) => {
  Vue.nextTick(() => {
    let { visible, destroyOnClose } = vnode.componentInstance
    // 防止未定义 destroyOnClose 关闭弹窗时dom未被销毁，指令被重复调用
    if (!visible) return
    let modal = el.getElementsByClassName('ant-modal')[0]
    let header = el.getElementsByClassName('ant-modal-header')[0]
    let left = 0
    let top = 0
    // 未定义 destroyOnClose 时，dom未被销毁，关闭弹窗再次打开，弹窗会停留在上一次拖动的位置
    if (!destroyOnClose) {
      left = modal.left || 0
      top = modal.top || 0
    }
    // top 初始值为 offsetTop
    top = top || modal.offsetTop
    // 点击title部分拖动
    header.onmousedown = e => {
      let startX = e.clientX
      let startY = e.clientY
      header.left = header.offsetLeft
      header.top = header.offsetTop
      el.onmousemove = event => {
        let endX = event.clientX
        let endY = event.clientY
        modal.left = header.left + (endX - startX) + left
        modal.top = header.top + (endY - startY) + top
        modal.style.left = modal.left + 'px'
        modal.style.top = modal.top + 'px'
      }
      el.onmouseup = event => {
        left = modal.left
        top = modal.top
        el.onmousemove = null
        el.onmouseup = null
        header.releaseCapture && header.releaseCapture()
      }
      header.setCapture && header.setCapture()
    }
  })
}

export {
   dragModal 
}

2. 在main.js引入并注册自定义指令

import * as directives from '@/utils/directives.js'

Object.keys(directives).forEach(key=>{
  Vue.directive(key,directives[key])
})

3. 在使用a-modal的地方添加v-drag-modal

<a-modal
   :title='operateType == "add" ? "新增试验" : "编辑实验" '
   width="1300"
   :dialogStyle="{ top: '20px' }"
   :visible="innerVisible"
   :destroyOnClose="true"
   @ok='handleOk'
   @cancel="innerVisible = false"
   v-drag-modal>
   ....
 </a-modal>